1. Field of the Invention
The present invention relates to an organic luminescent device, and more particularly, to a blue emitting material of an emitting layer.
2. Description of the Related Art
Recently, with the trend of a large sized display, a request of a flat display that occupies a small area has been increased. One example of the flat display is an organic electroluminescent device also called as an organic light emitting diode (OLED). And, technology for the organic electroluminescent display is developed rapidly, whereby various prototypes have been in market already.
The organic electroluminescent device emits light in a manner that electric charges are injected in an organic layer formed between an anode and a cathode so as to form a pair of electron and hole to generate an exciton and an excited state of the exciton falls to a ground state so as to emit light.
The organic electroluminescent device is not only formed on a flexible transparent substrate such as a plastic but also operated at a lower voltage (less than 10V) compared to a plasma display panel or an inorganic electroluminescent display.
Also, the organic electroluminescent device has advantages in that power consumption is reduced and various colors are available.
Moreover, the organic electroluminescent device enables to express three colors including green, blue, and red. Therefore, many concerns are focused on the organic electroluminescent device as the next generation full color display.
The organic electroluminescent device may be realized to emit blue, green, or red light in accordance with a material forming the emitting layer.
Particularly, the emitting layer for blue luminescence is a host employing materials such as PBD and DPVBi and is fabricated by doping 1-3% of materials such as perylene, coumarine, and pyrene as a dopant.
However, it is a biggest problem in realizing blue luminescence of the organic electroluminescent device that a degree of color purity and the luminescence efficiency are lowered.
The conventional blue emitting materials emit light with a long wavelength during emission and had a problem of lowering the degree of color purity and the luminescence efficiency, and even more lowered at high doping density.